Conductive pastes are composite materials prepared from binders (e.g. resin) and conductive fillers (e.g. metal), which are well-known in the electronic industry. Such conductive pastes are simultaneously conductive (from the metal), and adhesive and viscous (from the resin), and the above properties can be adjusted according to process requirements. The conductivity of the conductive pastes depends on the type, shape, and size of the conductive fillers (such as metal powder). The conductive pastes with more contact area between the conductive fillers have a higher conductivity. Typical conductive pastes have a high content (>75 wt %) of conductive fillers interconnecting each other in an organic resin binder. After adhering or curing the conductive paste by thermal pressing, the conductive fillers may form a network link to form a contact with a top electrode and a bottom electrode, thereby forming a current path for signal transmission.
The conductive pastes are critical materials in electronic device packages, electrodes, and interconnect structures. The conductive pastes are usually classified into two major types: the high-temperature sintering type and the low-temperature curing types. The conductive pastes of the sintering type are often used in the solar-cell industry, and the conductive pastes of the curing type are widely used in printed circuits and electronic packages. Copper powder is an excellent conductive filler for the conductive paste, however, it is easily oxidized at temperatures of 200° C. and higher. As such, special conditions are required when sintering conductive pastes containing copper to form electrodes, such as performing the process under an inert gas (e.g. nitrogen) environment to prevent the copper from oxidizing.
Accordingly, a novel conductive paste composition with decreased copper oxidation is called for.